Fuel injection systems make it possible to meter the fuel needed for combustion in an internal combustion engine with the aid of one or multiple injectors. In the case of direct gasoline injection and common rail injection, the fuel is injected directly into the combustion chamber. For the combustion quality, and accordingly the fuel consumption and exhaust emissions of the internal combustion engine, the metered quantity of fuel is of crucial importance.
The metered quantity of fuel is, however, influenced by properties of the injector per se. Due to manufacturing tolerances, which occur in the injectors used within an internal combustion engine, the quantity of fuel metered by these injectors tends to vary, resulting in a reduced combustion quality. In particular in the so-called small quantity range (partial lift range, ballistic range), the impact of a relative manufacturing tolerance of the injectors is particularly severe. For addressing this problem, injector calibration methods are used in which a relationship between activation period (ti) and injection quantity (q) is established injector-individually in order to be able to use this relationship for future injections.
Various injector calibration methods are described in German Patent Application Nos. DE 10 2009 003 212 A1 and DE 10 2009 003 211 A1. These methods are, however, highly complex in terms of regulation technology, so that measured variables for the regulation are ascertained for each activation operation.
It is desirable to simplify the injector calibration.